U.S. Pat. No. 2,514,469 to Burkhardt discloses a heat exchanger which includes one pre-formed metal plate with a plurality of corrugations or deformed areas into which pressurized water is injected to clean solder from existing passageways. A series flow passageway is established between superimposed sheet metal portions as a result of the bonding material being applied in a particular pattern to one of the sheet metal portions. Other areas of the sheets are plated with copper or zinc and covered with chromium to prevent them from being bonded.
U.S. Pat. No. 2,421,607 to Fowler discloses a method of making a metallic printing screen by laminating a solder coated screen and solder coated plate under pressure while the solder is plastic.
U.S. Pat. No. 4,021,901 to Kleine et al discloses a method for manufacturing a heat exchanger from metal sheets having a weld inhibiting material applied to one of the sheets. The sheets are clamped together and pressure-welded and hot-dashed rolled. The portions which do not weld together because of the weld-inhibiting material are then inflated by introducing air or water to form a system of internal tubular passageways.
U.S. Pat. No. 3,394,446 to Valyi discloses the method of forming a composite metal structure which includes a weld-inhibiting material. Because of the weld-inhibiting material, a pattern of passageways may be formed by the injection of fluid into areas in which welding was inhibited.
U.S. Pat. No. 3,483,616 to Shomphe discloses a method for forming a printed circuit board. An insulating board having conductor patterns on both sides and eyelet connector holes between the patterns is coated with a protected coating and then passed through a soldering machine. Solder is applied on the unprotected areas of the conductor pattern.
U.S. Pat. No. 3,048,916 to Gahlinger discloses a method of making welded passageway panels. A weld-resist pattern is printed on one-half of a metal sheet which is then folded over and subjected to high temperature and pressure. The unwelded area is then pressure-expanded to form passageways.